0.29Pb(Mg1/2W1/2)O3-0.41Pb(Ni1/3Nb2/3)O3-0.30PbTiO3 + 0.002 5MnO2 + xWO3(PMW-PNN-PT) ceramics were prepared by Semichemical Method. The Mg(Ac)2, Ni(Ac)2, and Mn(NO)3 solution rather than MgO, NiO and MnO2 were added to the slurry of PbO, WO3, Nb2O5 and TiO2 and then calcined at 850 °C for 2 h. Then the sample was sintered at 1 100～1 200 °C for 2 h. The effect of sintering temperature and WO3-excess amounts on the phase constitute, microstructure and the dielectric characteristics was investigated. The result showed that the PMW-PNN-PT powders with pure pervoskite phase were prepared by single-step calcination. The development of sintered temperature contributes to the increase of dielectric constant and the flatness of dielectric temperature dependence. But the dielectric properties will be worse if the sintered temperature is too high. The increase of WO3-excess level lead to an increase of Pb2WO5 phase and the flatness of dielectric curves, but the dielectric constant will be decreased. The proper WO3-excess amount of X7R type PMW-PNN-PT ceramics is 5mol% and the proper sintering condition is 1 150 °C for 2 h, the maximum dielectric constant is 5 395.
